1. Field of the Invention
Aspects of the present invention relate to an inkjet printable electrode composition, an electrode including the same, and a secondary battery including the electrode, and more particularly, to an inkjet printable electrode composition, which is to be used to form a thin electrode, an electrode including the same, and a secondary battery including the electrode.
2. Description of the Related Art
Recently, demands for secondary batteries as a power source for portable electrical devices, such as mobile phones, personal digital assistants (PDAs), or portable multimedia players (PMP); as a power source to drive a motor of high-performance hybrid vehicles or electric vehicles; as a power source for flexible displays, such as e-inks, e-papers, flexible liquid crystal display devices (LCDs), or flexible organic light emitting diode (OLED) displays, are increasing rapidly. In the future, secondary batteries will be used as a power source for integrated circuit devices on a printed circuit board. However, when secondary batteries are used as a power source for portable electrical devices, there are limitations on product designs due to packaging requirements to obtain stability. To be used as a power source to drive a motor, secondary batteries should be prepared to be high performance, small, and lightweight. To be used as a power source for flexible displays, secondary batteries should be prepared to be thin, lightweight, and flexible. To be used as a power source for integrated circuit devices, secondary batteries should be patterned to a predetermined shape.
Such various properties required of the secondary batteries can be obtained using an inkjet printing method instead of a conventional slurry coating method. The inkjet printing method is suitable to provide a thin, uniform, and planarized pattern of an electrode for a secondary battery at low costs.
Such an inkjet printing method allows a user to print a desired pattern having relatively high resolution at low costs. Due to the advantages of inkjet printing, inkjet printing methods have been used in home and office printers. According to the inkjet printing method, ink is ejected in a drop-on-demand manner, i.e., ink is ejected in a predetermined amount at a predetermined location. Therefore, the inkjet printing method is efficient in terms of ink consumption and environmentally friendly, and thus, the inkjet printing method is used in a wide range of industrial applications including forming electrodes for displays or color filters.
An inkjet printer, which is operated using the inkjet printing method, may perform its printing process using a thermal spraying method in which bubbles are formed and ink is ejected by a force generated when bubbles are formed and a piezo method in which intensity of a current is adjusted using a piezo actuator and ink is ejected. In the thermal spraying method and the piezo method, nozzles can be easily clogged by particles of ink when the ink is ejected, because the size of nozzles is as small as 20-50 μm. To stably eject ink, a moisturizer (or a wetting agent), such as glycol or glycerol, is used in a great amount to hinder evaporation of ink at nozzles.
However, when a conventional ink for inkjet printing is used to form a pattern for an electrode, the viscosity of the ink is increased due to the addition of a binder which increases a binding force between a collector and electrode forming components and protects the formed electrode when the electrode swells or shrinks during charging and discharging. Therefore, it is difficult to eject the ink through a nozzle due to such high viscosity of the ink.